Polyolefin multilayer pipe

ABSTRACT

Polyolefin multilayer pipes consisting at least one of the layers of a β-nucleated propylene homopolymer and/or β-nucleated copolymers from 90.0 to 99.9% by weight of propylene and 0.1 to 10.0% by weight of α-olefins. The pipes are to be classified in ring stiffness class ≧4. The pipes are suitable for non pressure pipe applications, preferably for outdoor use, for above as well as underground drainage and sewerage pipe systems, surface water pipes, pipes for cable protection, pipes for cold climate conditions and for indoor use, soil and waste water pipes.

FIELD OF THE INVENTION

[0001] The invention relates to polyolefin multilayer pipes, fittings,chambers and the like wherein at least one of the layers comprises aβ-nucleated propylene polymer, as well as a process for producing them.

BACKGROUND OF THE INVENTION

[0002] Polyolefin multilayer pipes wherein at least one of the layers ofthe multilayer pipe comprises a propylene polymer are known.

[0003] WO 98/43806 discloses a multilayer plastic tube, comprising abase tube consisting of a propylene polymer, a barrier layer coating thebase tube, and a protective layer, containing a lubricant, applied ontop of the barrier layer.

[0004] WO 97/33117 discloses a multilayer pipe with at least two layersof different plastic materials, in which one layer consists of aZiegler-Natta propylene copolymer, optionally with 1-30% by weightelastomer content.

[0005] The disadvantage of these multilayer pipes is the insufficientbalance of high stiffness and good impact properties, especially at lowtemperatures.

OBJECT OF THE INVENTION

[0006] It is the object of the present invention to provide polyolefinmultilayer pipes, where at least one of the layers of the multilayerpipe comprises a β-nucleated propylene polymer, with a superiorcombination of high stiffness and good impact properties, especially atlow temperatures.

BRIEF DESCRIPTION OF THE INVENTION

[0007] According to the present invention, this object is achieved bypolyolefin multilayer pipes where at least one of the layers of themultilayer pipe comprises a propylene homopolymer with melt indices of0.05 to 10 g/10 min at 230° C./2.16 kg or propylene copolymers from 90.0to 99.9% by weight of propylene and 0.1 to 10.0% by weight of α-olefinswith 2 or 4 to 18 carbon atoms with melt indices of 0.05 to 15 g/10 minat 230° C./2.16 kg, or mixtures thereof, wherein the propylenehomopolymers and/or propylene copolymers are β-nucleated propylenepolymers and the multilayer pipe with a pipe diameter of less than 0.25m has an impact energy E_(D) (normalised) of at least 400 Nm/m and aring stiffness S determined according to ISO 9969 ≧4 kN/m² and amultilayer pipe with a pipe diameter of ≧0.25 m has an impact energy Eof at least 120 Nm and a ring stiffness S determined according to ISO9969 ≧4 kN/m².

[0008] β-nucleated propylene polymers are isotactic propylene polymerscomposed of chains in a 3₁ helical conformation having an internalmicrostructure of β-form spherulites being composed of radial arrays ofparallel stacked lamellae. This microstructure can be realized by theaddition of β-nucleating agents to the melt and crystallization. Thepresence of the β-form can be detected through the use of wide angleX-ray diffraction (Moore, J., Polypropylene Hand-book, p. 134-135,Hanser Publishers Munich 1996).

[0009] According to an advantageous feature of the present invention theβ-nucleated propylene polymers in at least one of the layers of themultilayer pipe are β-nucleated propylene homopolymers having anIR_(τ)≧0.98, a tensile modulus of ≧1500 MPa at +23° C. and a Charpyimpact strength, using notched test specimens, at −20° C. ≧3 kJ/m²and/or β-nucleated propylene block copolymers having an IR_(τ) of thepropylene homopolymer block of ≧0.98, a tensile modulus of ≧1100 MPa at+23° C. and a Charpy impact strength ≧6 kJ/m² at −20° C. using notchedtest specimens.

[0010] The IR_(τ) of the propylene polymers is measured and calculatedas described in EP 0 277 514 A2 on page 5 (column 7, line 53 to column8, line 11).

[0011] According to a preferred embodiment the β-nucleated propylenehomopolymers or the propylene homopolymer block of the β-nucleatedpropylene block copolymers have an IR_(τ) of ≧0.985. The difference of0.005 in IR_(τ), IR_(τ) being a measure for isotacticity, encompasses asignificant increase in mechanical polymer properties, especially instiffness.

[0012] The propylene homopolymers used in at least one layer of themultilayer pipe according to the present invention have melt indices of0.05 to 15 g/10 min at 230° C./2.16 kg, preferably 0.1 to 8 g/10 min at230° C./2.16 kg, most preferably 0.2 to 5 g/10 min at 230° C./2.16 kg.

[0013] The propylene copolymers have melt indices of 0.05 to 20 g/10 minat 230° C./2.16 kg, preferably 0.1 to 8 g/10 min at 230° C./2.16 kg,most preferably 0.2 to 5 g/10 min at 230° C./2.16 kg.

[0014] According to the present invention the propylene homopolymersused for at least one layer of the multilayer pipe show a tensilemodulus ≧1500 MPa, preferably ≧1600 MPa and the propylene copolymersshow a tensile modulus ≧1100 MPa, preferably ≧1300 MPa and mostpreferably ≧1500 MPa.

[0015] The propylene homopolymers according to the present inventionhave a Charpy impact strength of ≧3 kJ/m² at −20° C., preferably 4 to 10kJ/m² at −20° C., most preferably 5 to 10 kJ/m² at −20° C.

[0016] The propylene copolymers according to the present invention havea Charpy impact strength of ≧6 kJ/m² at −20° C., preferably ≧9kJ/m² at−20° C., most preferably ≧10 kJ/m² at −20° C. Charpy impact strength ofup to at least 60 kJ/m² is possible for copolymers used for theproduction of at least one layer of the multilayer pipe according to theinvention.

[0017] According to a preferred embodiment of the present invention theβ-nucleated propylene polymers with an IR_(τ)≧0.98 in at least one ofthe layers of the multilayer pipe being propylene polymers obtained bypolymerization with a Ziegler-Natta catalyst system comprisingtitanium-containing solid components, an organoalumina, magnesium ortitanium compound as cocatalyst and an external donor according to theformula

R_(x)R′_(y)Si(MeO)_(4-x-y),

[0018] wherein R and R′ are identical or different and are branched orcyclic aliphatic or aromatic hydrocarbon residues, and y and xindependently from each other are 0 or 1, provided that x+y are 1 or 2.

[0019] Example of propylene polymers with high stereospecifity obtainedby polymerization with a Ziegler-Natta catalyst system, are propylenepolymers as described in WO 99/24478 and WO 99/16797.

[0020] A preferred external donor in the Ziegler-Natta catalyst systemfor producing the propylene polymers with high stereospecifity comprisedat least in one of the layers of the multilayer pipe isdicyclopentyldimethoxysilane.

[0021] According to an advantageous embodiment of the present inventionthe β-nucleated propylene polymer contains 0.0001 to 2.0 wt %, based onthe polypropylenes used,

[0022] dicarboxylic acid derivative type diamide compounds fromC₅-C₈-cycloalkyl monoamines or C₆-C₁₂-aromatic monoamines andC₅-C₈-aliphatic, C₅-C₈-cycloaliphatic or C₆-C₁₂-aromatic dicarboxylicacids, and/or

[0023] diamine derivative type diamide compounds from C₅-C₈-cycloalkylmonocarboxylic acids or C₆-C₁₂-aromatic monocarboxylic acids andC₅-C₈-cycloaliphatic or C₆-C₁₂-aromatic diamines, and/or

[0024] amino acid derivative type diamide compounds from amidationreaction of C₅-C₈-alkyl-, C₅-C₈-cycloalkyl- or C₆-C₁₂-arylamino acids,C₅-C₈-alkyl-,C₅-C₈-cycloalkyl- or C₆-C₁₂-aromatic monocarboxylic acidchlorides and C₅-C₈-alkyl-, C₅-C₈-cycloalkyl- or C₆-C₁₂-aromaticmono-amines, and/or

[0025] quinacridone derivative compounds of the type quinacridonecompounds, quinacridonequinone compounds, and/or dihydroquinacridonetype compounds, and/or

[0026] dicarboxylic acid salts of metals from group IIa of periodicsystem and/or mixtures of dicarboxylic acids and metals from group IIaof periodic system, and/or

[0027] salts of metals from group IIa of periodic system and imido acidsof the formula

[0028] wherein x=1 to 4; R=H, —COOH, C₁-C₁₂-alkyl, C₅-C₈-cycloalkyl orC₆-C₁₂-aryl, and Y=C₁-C₁₂-alkyl, C₅-C₈-cycloalkyl orC₆-C₁₂-aryl-substituted bivalent C₆-C₁₂-aromatic residues,

[0029] as β-nucleating agent.

[0030] Example of the dicarboxylic acid derivative type diamidecompounds from C₅-C₈-cycloalkyl monoamines or C₆-C₁₂-aromatic monoaminesand C₅-C₈-aliphatic, C₅-C₈-cycloaliphatic or C₆-C₁₂-aromaticdicarboxylic acids, optionally contained in the β-nucleated propylenepolymers of at least one of the layers of the multilayer pipe, are

[0031] N,N′-di-C₅-C₈-cycloalkyl-2,6-naphthalene dicarboxamide compoundssuch as N,N′-dicyclohexyl-2,6-naphthalene dicarboxamide andN,N′-dicyclooctyl-2,6-naphthalene dicarboxamide,

[0032] N,N′-di-C₅-C₈-cycloalkyl-4,4-biphenyldicarboxamide compounds suchas N,N′-dicyclohexyl-4,4-biphenyldicarboxamide andN,N′-dicyclopentyl-4,4-biphenyldicarboxamide,

[0033] N,N′-di-C₅-C₈-cycloalkyl-terephthalamide compounds such asN,N′-dicyclohexylterephthalamide and N,N′-dicyclopentylterephthalamide,

[0034] N,N′-di-C₅-C₈-cycloalkyl-1,4-cyclohexanedicarboxamide compoundssuch as N,N′-dicyclohexyl-1,4-cyclohexanedicarboxamide andN,N′-dicyclohexyl-1,4-cyclopentanedicarboxamide.

[0035] Example of the diamine derivative type diamide compounds fromC₅-C₈-cycloalkyl monocarboxylic acids or C₆-C₁₂-aromatic monocarboxylicacids and C₅-C₈-cycloaliphatic or C₆-C₁₂-aromatic diamines, optionallycontained in the β-nucleated propylene polymers of at least one of thelayers of the multilayer pipe, are

[0036] N,N′-C₆-C₁₂-arylene-bis-benzamide compounds such asN,N′-p-phenylene-bis-benzamide and N,N′-1,5-naphthalene-bis-benzamide,

[0037] N,N′-C₅-C₈-cycloalkyl-bis-benzamide compounds such asN,N′-1,4-cyclopentane-bis-benzamide andN,N′-1,4-cyclohexane-bis-benzamide.

[0038] N,N′-p-C₆-C₁₂-arylene-bis-C₅-C₈-cycloalkylcarboxamide compoundssuch as N,N′-1,5-naphthalene-bis-cyclohexanecarboxamide andN,N′-1,4-phenylene-bis-cyclohexanecarboxamide.

[0039] N,N′-C₅-C₈-cycloalkyl-bis-cyclohexanecarboxamide compounds suchas N,N′-1,4-cyclopentane-bis-cyclohexanecarboxamide andN,N′-1,4-cyclohexane-bis-cyclohexanecarboxamide.

[0040] Example of the amino acid derivative type diamide compounds,optionally contained in the β-nucleated propylene polymers of at leastone of the layers of the multilayer pipe, are

[0041] N-phenyl-5-(N-benzoylamino)pentaneamide and/or

[0042] N-cyclohexyl-4-(N-cyclohexylcarbonylamino)benzamide.

[0043] Example of the quinacridone type compounds, optionally containedin the β-nucleated propylene polymers of at least one of the layers ofthe multilayer pipe, are quinacridone, dimethylquinacridone and/ordimethoxyquinacridone.

[0044] Example of the quinacridonequinone type compounds, optionallycontained in the β-nucleated propylene polymers of at least one of thelayers of the multilayer pipe, are quinacridonequinone, a mixed crystalof 5,12-dihydro(2,3b)acridine-7,14-dione withquino(2,3b)acridine-6,7,13,14-(5H,12H)-tetrone as disclosed in EP-B 0177 961 and/or dimethoxyquinacridonequinone.

[0045] Example of the dihydroquinacridone type compounds, optionallycontained in the β-nucleated propylene polymers of at least one of thelayers of the multilayer pipe, are dihydroquinacridone,dimethoxydihydroquinacridone and/or dibenzodihydroquinacridone.

[0046] Example of the dicarboxylic acid salts of metals of group IIa ofperiodic system, optionally contained in the β-nucleated propylenepolymers of at least one of the layers of the multilayer pipe, arepimelic acid calcium salt and/or suberic acid calcium salt.

[0047] Example of salts of metals from group IIa of periodic system andimido acids of the formula

[0048] are the calcium salts of phthaloylglycine,hexahydrophthaloylglycine, N-phthaloylalanine and/orN-4-methylphthaloylglycine.

[0049] A still further embodiment of the present invention is a 3-layerpipe, wherein the outer and inner layer of the pipe comprises aβ-nucleated propylene polymer and the mid layer comprises a recycledpropylene polymer, a propylene polymer of higher stiffness than theβ-nucleated propylene polymer, and/or a propylene polymer containingfillers.

[0050] A still further embodiment of the present invention is a 2-layerpipe, wherein the outer layer of the pipe comprises a β-nucleatedpropylene polymer and the inner layer comprises a recycled propylenepolymer, a propylene polymer of higher stiffness than the β-nucleatedpropylene polymer and/or a propylene polymer containing fillers.

[0051] Preferred propylene polymers of higher stiffness than theβ-nucleated propylene polymer in the mid layer of the 3-layer pipe or inthe inner layer of the 2-layer pipe are α-nucleated propylenehomopolymers and/or copolymers from 90.0 to 99.9% by weight of propyleneand 0.1 to 10.0% by weight of α-olefins with 2 or 4 to 18 carbon atoms.

[0052] Preferred α-nucleating agents, contained from 0.05 to 2% byweight in the propylene polymers of higher stiffness, are dibenzylidenesorbitol, derivatives of sorbitol and/or diphenylglycine; salts ofC₆-C₁₈ aliphatic or C₇-C₁₃ aromatic carbonic acids, selected from sodiumbenzoate, tert.-butylbenzoic acid alumina salt and/or long chainC₈-C₁₈-carbonic acid salts; phosphoric acid derivatives, selected fromammonium polyphosphate, cyclic calcium phosphate compounds,sodium-2,2′-methylenebis-(4,6-di-tert.-butylphenyl)phosphate and/orbis(tert.-butyl)-phosphoric acid sodium salt; and/or talc.

[0053] Further polymers of higher stiffness may be polymers differentfrom isotactic propylene polymers, selected from the group, oftetrafluoroethylene polymers, polycarbonates, polybutyleneterephthalate,polyethyleneterephthalate, 3-methyl-butene polymers,4-methylpentene-1-polymers, syndiotactic propylene polymers,polyphenyleneoxides, propylene methylbutene copolymers, styreneacrylonitrile copolymers, poly-allyltrimethylsilanes and/or hydrolysedethylene vinylacetate copolymers.

[0054] Preferred fillers contained in the propylene polymers of the midlayer of the 3-layer pipe or in the inner layer of the 2-layer pipe areAl₂O₃, Al(OH)₃, barium sulfate, calcium carbonate, glass beads, woodflour, silica, hollow microspheres, carbon black, talcum, bentonite,mica and/or wollastonite.

[0055] A further object of the present invention is a process forproducing polyolefin multilayer pipes by extrusion or injection moldingprocesses where at least one of the layers of the multilayer pipecomprises a propylene homopolymer with melt index of 0.05 to 10 g/10 minat 230° C./2.16 kg and/or copolymers from 90.0 to 99.9% by weight ofpropylene and 0.1 to 10.0% by weight of α-olefins with 2 or 4 to 18carbon atoms with melt indices of 0.05 to 15 g/10 min at 230° C./2.16kg, wherein the propylene homopolymers and/or propylene copolymers areβ-nucleated propylene polymers.

[0056] In the production of polyolefin multilayer pipes according to theinvention conventional extruders are suitable. For example, thepolyolefin layers may be manufactured with single screw extruders withan L/D of 20 to 40 or twin screw extruders or other types of extruders,suitable for multilayer extrusion, as described for example in U.S. Pat.No. 5,387,386 and FI 83184. Optionally, a melt pump and/or a staticmixer can be used additionally between the extruder and the ring diehead. Ring shaped dies with diameters ranging from approximately 20 to2000 mm and even greater are possible. Advantageous die temperatures fordischarging the melt are 180 to 240° C. After leaving the ring-shapeddie, the polyolefin multilayer plastic pipes are taken off over acalibrating sleeve and cooled.

[0057] The multilayer pipe can also be manufactured in extrusion windingprocesses in diameters up to 3 to 4 meters or even larger.

[0058] The pipes may also be processed in corrugating devices incombination or close to the calibration step, for example formanufacturing of multilayer pipes of corrugated double/triple walldesign with or without hollow sections or multilayer pipes with ribbeddesign.

[0059] The known methods of multilayer pipe extrusion or injectionmolding are described for instance, in Djordjevic, D., “Coextrusion”,Rapra Review Reports, Vol. 6, No. 2, 1992, pp 51-53, or PlasticExtrusion technology, Hanser Publishers 1997, Chapter 3 (F. Hensen).

[0060] For producing the polyolefin multilayer pipes according to theinvention, usual auxiliary materials e.g. 0.01 to 2.5 wt % stabilizers,0.01 to 1 wt % processing aids, 0.1 to 1 wt % antistatic agents and 0.2to 3 wt % pigments, in each case based on the olefin polymers used, maybe used.

[0061] As stabilizers preferably mixtures of 0.01 to 0.6 wt % phenolicantioxidants, 0.01 to 0.6wt % 3-arylbenzofuranones, 0.01 to 0.6 wt %processing stabilizers based on phosphites, 0.01 to 0.6 wt % hightemperature stabilizers based on disulfides and thioethers and/or 0.01to 0.8 wt % sterically hindered amines (HALS) are suitable.

[0062] According to a feature of the present invention the β-nucleatedpropylene polymers for use in at least one layer of the multilayer pipeare propylene polymers produced by melt mixing propylene homopolymersand/or propylene copolymers with 0.01 to 2.0% by weight, based on thepolypropylenes used, D-nucleating agents at temperatures from 175 to250° C.

[0063] Preferred applications of polyolefin multilayer pipes are nonpressure pipe applications, preferably for outdoor use, for above aswell as underground drainage and sewerage pipe systems, surface waterpipes, pipes for cable protection, pipes for cold climate conditions andfor indoor use, soil and waste water pipes.

[0064] The advantage of the polyolefin multilayer pipes according to theinvention is the possibility to produce tailor-made polyolefin pipes,fittings, chambers and the like with a superior combination of highstiffness and good impact properties, especially at low temperatures.The layer of β-nucleated propylene polymer allows thinner pipe walls ofthe polyolefin multilayer pipes, utilizing larger amounts of highstiffness propylene polymers in the mid layers, and using larger amountsof recycled propylene polymers and fillers in the mid layers.

[0065] For practical testing of the impact resistance, the pipes weresubjected to external blows by the staircase method according to EN1411. In this test, a series of the polyolefin multilayer pipes wereconditioned at 0° C. and subjected to a hammer with a striker type d 90falling from different heights. As a result, H₅₀[=m] indicates theheight, at which 50% of the pipes fail.

[0066] The energy E of the striker is calculated according to theformula

E=m.g.H ₅₀

[0067] wherein m is the mass of the striker in kg (normally between 4and 12.5 kg) and g is the gravitational acceleration (9.81 m/s²) and H₅₀is the height in meter from which the striker is dropped, when 50% ofthe pipes fail.

[0068] The energy E_(D) normalized for different pipe diameters can becalculated as the energy E divided by the outer diameter of the pipe (inmeter).

[0069] For pipes with outer diameters of less than 0.25 m it isdesirable that the impact energy E_(D) is at least 400 Nm/m, preferably≧600 Nm/m, more preferably ≧800 Nm/m, most preferably ≧1000 Nm/m.

[0070] For pipes with outer diameters of ≧0.25 m the pipe dimensions arenormally relatively thinner and it is desirable that the energy E is atleast 120 Nm, preferably ≧180 Nm, more preferably ≧240 Nm and mostpreferably ≧300 Nm.

[0071] Ring stiffness tests have been performed according to ISO 9969 at+23° C. According to the thus determined ring stiffness values the pipesmay be classified in ring stiffness classes which are 2, 4, 8, 10,16, 20etc.

[0072] Pipes according to the invention will be classified at least asring stiffness class 4.

[0073] It has also been found that with certain pipes according to thepresent invention it is possible to avoid the stress whiteningphenomenon as is normally seen for pipes from polypropylene blockcopolymer materials.

[0074] Stress whitening is due to cavitational effects, i. e. the volumecontraction of the material during cooling is different in the amorphousrubber phase compared with the PP-homopolymer matrix. When sufficientstrain or stress is applied on the material, cavities in the interfacewill appear which will scatter light. This will give an opticalwhitening effect in the material, but for this it is necessary to eitherelongate the material to around the yield point, or alternatively hit(impact) the material, which for example could happen during roughinstallation/transport or during processing (process elongation duringmanufacturing of inline sockets, during manufacturing of corrugatedpipes etc).

[0075] Thus, the beneficial properties of polypropylenes and betanucleated polypropylenes, and especially the good impact properties ofbeta nucleated propylene homopolymer, can be utilised, without havingthe negative effect of stress whitening as it would be the case whenusing a propylene block copolymer material (alpha or beta nucleated) inorder to get sufficient impact properties. Stress whitening is alsoreduced with beta nucleated propylene block copolymers compared withalpha nucleated propylene block copolymers, due to the difference incrystal density (alpha=0.936 and beta=0.921). With the materialsaccording to the invention the stiffness is also high.

[0076] A further preferred embodiment of the present invention istherefore a multilayer pipe with reduced stress whitening, where atleast an inner or outer layer (or both) is comprised of a β-nucleatedpolypropylene homopolymer and/or propylene block copolymer as it is usedaccording to the invention. By using such beta nucleated propylenepolymers there will be a reduced or no whitening effect but still goodimpact and stiffness as well as other properties. Still higher stiffnesslevels can be achieved by, for example, a mid leayer, which is comprisedof e.g. a-nucleated and/or filled material.

EXAMPLES

[0077] The following tests were made using injection molded testspecimen prepared according to ISO 1873

[0078] Tensile modulus according to ISO 527 (cross head speed 1 mm/min)at +23° C.

[0079] Charpy impact strength, notched, according to ISO 179/1 eA

[0080] Impact resistance according to EN 1411 (staircase method, strikerd 90, H₅₀-value at 0° C./4.0 kg)

[0081] Ring stiffness according to ISO 9969 at +23° C.

Example 1

[0082] 1.1 Preparation of the β-Nucleated Propylene Polymer

[0083] A Mixture of

[0084] 90 wt % of a propylene block copolymer, obtained by combined bulkand gas phase polymerization using a Ziegler-Natta catalyst system withdicyclopentyldimethoxysilane as external donor, having an ethylenecontent of 8.3 wt %, an IR_(τ) of the propylene homopolymer block of0.985 and a melt index of 0.30 g/10 min at 230° C./2.16 kg,

[0085] 10% by weight of a master batch comprising 99 parts by weight ofa propylene block copolymer having an ethylene content of 8.3 wt %, anIR_(τ) of the propylene homopolymer block of 0.985, and a melt index of0.30 g/10 min at 230° C./2.16 kg, and 1 part by weight of pimelic acidcalcium salt, and 0.1 wt % calcium stearate, 0.1 wt %tetrakis[methylene(3,5-di-t-butylhydroxyhydrocinnamate)]methane and 0.1wt % tris-(2,4-di-t-butylphenyl)phosphite, based on the sum of thepropylene polymers used, is melted in a twin screw extruder with atemperature profile of 100/145/185/210/220/225/225/225/220/200/185° C.,homogenized, discharged and pelletized.

[0086] The resulting polypropylene polymer has a melt index of 0.32 g/10min at 230° C./2.16 kg, a tensile modulus of 1290 MPa and a Charpyimpact strength, using notched test specimens, at −20° C. of 39 kJ/m².

[0087] 1.2 Manufacture of the Polyolefin 2-Layer Pipe

[0088] For manufacturing the polyolefin multilayer pipes, a conventionalpipe extruder having a screw diameter of 60 mm, L/D=28, and oneconventional side extruder having a screw diameter of 50 mm, allconnected to a multilayer tool of conventional design, having thepossibility of extruding 1-3 layers of varying thickness of thematerials and composition of the layers, was used. The pipes werecalibrated and cooled by means of a conventional downstream equipment.

[0089] For producing the 2-layer pipe, the 60 mm extruder (temperatureprofile 200/230/230/ 230/230/230/210/210° C.) for the inner layer wasfed with a recycled mixed propylene polymer (melt index 0.5 g/10 min at230° C./2.16 kg), and a 50 mm side extruder (temperature profile180/200/225/225/210° C.) for the outer layer was fed with theβ-nucleated propylene polymer of 1.1.

[0090] 1.2.1.

[0091] The resulting 2-layer pipe, produced at a line speed of 1.1m/min, has an outer diameter of 110 mm and an wall thickness of 5.2 mm.Thickness of the outer layer was 1.9 mm and of the inner layer 3.3 mm.

[0092] Energy E_(D) was ≧1070 Nm/m and ring stiffness was 11.7 kN/m².

[0093] 1.2.2.

[0094] A further 2 layer pipe, produced at a line speed of 1.1 m/min hasan outer diameter of 110 mm and a wall thickness of 4.1 mm. Thickness ofthe outer layer was 1.0 mm and of the inner layer 3.1 mm.

[0095] Energy E_(D) was ≧620 Nm/m and ring stiffness was 6 kN/m².

[0096] 1.2.3

[0097] A further 2 layer pipe, produced at a line speed of 1.1 m/min hasan outer diameter of 110 mm and a wall thickness of 3.5 mm. Thickness ofthe outer layer was 1.0 mm and of the inner layer 2.5 mm.

[0098] Energy E_(D) was ≧470 Nm/m and ring stiffness was 4.2 kN/m².

Example 2

[0099] 2.1 Preparation of the β-Nucleated Propylene Polymer

[0100] A mixture of

[0101] 94 wt % of a propylene homopolymer, obtained by bulkpolymerization using a Ziegler-Natta catalyst system withdicyclopentyldimethoxysilane as external donor, having an IR_(τ) of0.985 and a melt index of 0.2 g/10 min at 230° C./2.16 kg, 6 wt % of amaster batch comprising 99.8 parts by weight of a propylene blockcopolymer having an ethylene content of 8.3% by weight, an IR_(τ) of thepropylene homopolymer block of 0.985, and a melt index of 0.30 g/10 minat 230° C./2.16 kg, and 0.2 parts by weight of a mixed crystal of5,12-dihydro(2,3b)acridine-7,14-dione withquino(2,3b)acridine-6,7,13,14-(5H,12H)tetrone, and 0.05 wt % magnesiumstearate, 0.1 wt %tetrakis[methylene(3,5-di-t-butyl-hydroxyhydrocinnamate)]methane and 0.1wt % tris-(2,4-di-t-butyl-phenyl)-phosphite, based on the sum of thepropylene polymers used, is melted in a twin screw extruder with atemperature profile of 100/145/190/215/225/230/230/215/205/190° C.,homogenized, discharged and pelletized.

[0102] The resulting polypropylene polymer has a melt index of 0.22 g/10min at 230° C./2.16 kg, a tensile modulus of 1335 MPa and a Charpyimpact strength, using notched test specimens, at −20° C. of 35 kJ/m².

[0103] 2.2 Manufacture of the Polyolefin Multilayer Pipe

[0104] For producing the 3-layer pipe, the pipe extruder of 1.2 wasused. The 60 mm extruder (temperature profile200/230/230/230/230/230/210/210° C.) for the intermediate layer was fedwith a blend of 70% by weight of a block propylene-ethylene copolymer(melt index 0.5 g/10 min at 230° C./2.16 kg, 4.2% by weight of ethylene)and 30% by weight of talcum, and both 50 mm side extruders (temperatureprofile 180/200/225/225° C.) for the inner and outer layer were fed withthe β-nucleated propylene polymer of 2.1.

[0105] The resulting 3-layer pipe, produced at a line speed of 1.0m/min, has an outer diameter of 110 mm and an wall thickness of 3.8 mm.The thickness of the outer layer was 1.0 mm, of the intermediate layer1.8 mm and of the inner layer 1.0 mm. Energy E_(D) was ≧1070 Nm/m andring stiffness was 8.1 kN/m².

Example 3

[0106] 3.1 Preparation of the β-Nucleated Propylene Polymer

[0107] A Mixture of

[0108] 75 wt % of a propylene block copolymer obtained by combined bulkand gas phase polymerization using a Ziegler-Natta catalyst system withdicyclopentyldimethoxysilane as external donor, having an ethylenecontent of 8.3 wt %, an IR_(τ) of the propylene homopolymer block of0.985, and a melt index of 0.30 g/10 min at 230° C./2.16 kg, 25 wt % ofa master batch comprising 99.5 parts by weight of a propylene blockcopolymer having an ethylene content of 8.3 wt %, an IR_(τ) of thepropylene homopolymer block of 0.985 and a melt index of 0.30 g/10 minat 230° C./2.16 kg, and 0.5 parts by weight of hexahydrophthaloylglycinecalcium salt, and 0.1 wt % calcium stearate, 0.1 wt %tetrakis[methylene(3,5-di-t-butylhydroxyhydrocinnamate)]methane and 0.1wt % tris-(2,4-di-t-butylphenyl)phosphite, based on the sum of thepropylene polymers used, is melted in twin screw extruder with atemperature profile of 100/145/185/210/220/225/225/200/185° C.,homogenized, discharged and pelletized. The resulting polypropylenepolymer has a melt index of 0.32 g/10 min at 230° C./2.16 kg, a tensilemodulus of 1310 MPa and a Charpy impact strength, using notched testspecimens, at −20° C. of 37 kJ/m².

[0109] 3.2. Manufacture of the Polyolefin Multilayer Pipe

[0110] For producing the 2-layer pipe, the pipe extruder of 1.2 wasused. The 60 mm extruder (temperature profile 200/230/230/230/230/210°C.) for the inner layer was fed with a random propylene-ethylenecopolymer (melt index 0.25 g/10 min at 230° C./2.16 kg, 3.5% by weightof ethylene), and the 50 mm side extruder (temperature profile180/200/225/225/210° C.) for the outer layer was fed with theβ-nucleated propylene polymer of 3.1.

[0111] The resulting 2-layer pipe, produced at a line speed of 1.6m/min, has an outer diameter of 110 mm and an wall thickness of 5.0 mm.The thickness of both layers was 2.5 mm.

[0112] Energy E_(D) was ≧1070 Nm/m and ring stiffness was 10.1 kN/m².

Example 4

[0113] 4.1 Preparation of the β-Nucleated Propylene Polymer

[0114] A Mixture of

[0115] 93 wt % of a propylene homopolymer, obtained by bulkpolymerization using a Ziegler-Natta catalyst system withdicyclopentyldimethoxysilane as external donor, having an IR_(τ) of0.985 and a melt index of 0.2 g/10 min at 230° C./2.16 kg,

[0116] 7 wt % of a master batch comprising 99.8 parts by weight of apropylene block copolymer having an ethylene content of 8.3% by weight,an IR_(τ) of the propylene homopolymer block of 0.985, and a melt indexof 0.30 g/10 min at 230° C./2.16 kg, and 0.2 parts by weight of a mixedcrystal of 5,12-dihydro(2,3b)acridine-7,14-dione withquino(2,3b)acridine-6,7,13,14-(5H,12H)tetrone, and 0.05 wt % magnesiumstearate, 0.1 wt %tetrakis[methylene(3,5-di-t-butyl-hydroxyhydrocinnamate)]methane and 0.1wt % tris-(2,4-di-t-butyl-phenyl)-phosphite, based on the sum of thepropylene polymers used, is melted in a twin screw extruder with atemperature profile of 100/145/190/215/225/230/230/215/205/190° C.,homogenized, discharged and pelletized.

[0117] The resulting polypropylene polymer has a melt index of 0.22 g/10min at 230° C./2.16 kg, a tensile modulus of 1340 MPa and a Charpyimpact strength, using notched test specimens, at −20° C. of 36 kJ/m².

[0118] 4.2 Manufacture of the Polyolefin Multilayer Pipe

[0119] For producing the 3-layer pipe, the pipe extruder of 1.2 wasused. The 60 mm extruder (temperature profile200/230/230/230/230/230/210/210° C.) for the intermediate layer was fedwith a blend of 70% by weight of a block propylene-ethylene copolymer(melt index 0.5 g/10 min at 230° C./2.16 kg, 4.2% by weight of ethylene)and 30% by weight of talcum, and both 50 mm side extruders (temperatureprofile 180/200/225/225° C.) for the inner and outer layer were fed withthe β-nucleated propylene polymer of 4.1.

[0120] 4.2.1

[0121] The resulting 3-layer pipe, produced at a line speed of 1.0m/min, has an outer diameter of 110 mm and a wall thickness of 5.0 mm.The thickness of the outer layer was 1.0 mm, of the intermediate layer3.0 mm and of the inner layer 1.0 mm. Energy E_(D) was ≧1070 Nm/m andring stiffness was 17.0 kN/m².

[0122] 4.2.2

[0123] A further 3-layer pipe, produced at a line speed of 1.0 m/min,has an outer diameter of 110 mm and a wall thickness of 3.8 mm.Thickness of the outer layer was 0.5 mm, of the intermediate layer 2.8mm and of the inner layer 0.5 mm.

[0124] Energy E_(D) was ≧440 Nm/m and ring stiffness was 8.5 kN/m².

Example 5

[0125]5.1. Preparation of the β-nucleated propylene polymer

[0126] A Mixture of

[0127] 75 wt % of a propylene block copolymer obtained by combined bulkand gas phase polymerization using a Ziegler-Natta catalyst system withdicyclopentyldimethoxysilane as external donor, having an ethylenecontent of 8.3 wt %, an IR_(τ) of the propylene homopolymer block of0.985, and a melt index of 0.30 g/10 min at 230° C./2.16 kg, 25 wt % ofa master batch comprising 99.5 parts by weight of a propylene blockcopolymer having an ethylene content of 8.3 wt %, an IR_(τ) of thepropylene homopolymer block of 0.985 and a melt index of 0.30 g/10 minat 230° C./2.16 kg, and 0.5 parts by weight of hexahydrophthaloylglycinecalcium salt, and 0.1 wt % calcium stearate, 0.1 wt %tetrakis[methylene(3,5-di-t-butylhydroxyhydrocinnamate)]methane and 0.1wt % tris-(2,4-di-t-butylphenyl)phosphite, based on the sum of thepropylene polymers used, is melted in twin screw extruder with atemperature profile of 100/145/185/210/220/225/225/200/185° C.,homogenized, discharged and pelletized. The resulting polypropylenepolymer has a melt index of 0.32 g/10 min at 230° C./2.16 kg, a tensilemodulus of 1310 MPa and a Charpy impact strength, using notched testspecimens, at −20° C. of 37 kJ/m².

[0128] 5.2. Manufacture of the Polyolefin Multilayer Pipe

[0129] For producing the 2-layer pipe, the pipe extruder of 1.2 wasused. The 60 mm extruder (temperature profile 200/230/230/230/230/210°C.) for the inner layer was fed with a mixture of 70% randompropylene-ethylene copolymer (melt index 0.25 g/10 min at 230° C./2.16kg, 3.5% by weight of ethylene), with 30% talc and the 50 mm sideextruder (temperature profile 180/200/225/225/210° C.) for the outerlayer was fed with the β-nucleated propylene polymer of 3.1.

[0130] The resulting 2-layer pipe, produced at a line speed of 1.6m/min, has an outer diameter of 110 mm and an wall thickness of 4.2 mm.The thickness of both layers was 2.1 mm.

[0131] Energy E_(D) was ≧1070 Nm/m and ring stiffness was 9.9 kN/m².

Example 6

[0132] 6.1 Preparation of the β-Nucleated Propylene Polymer

[0133] A Mixture of

[0134] 95 wt % of a propylene homopolymer, obtained by bulk phasepolymerization using a Ziegler-Natta catalyst system withdicyclopentyldimethoxysilane as external donor, having an IR_(τ) of0.987 and a melt index of 1.1 g/10 min at 230° C./2.16 kg,

[0135] 5 wt % of a master batch comprising 97.5 parts by weight of apropylene homopolymer having an IR_(τ) of 0.987 and a melt index of 4.2g/10 min at 230° C./2.16 kg, and 2.5 parts by weight ofN,N′-dicyclohexyl-2,6-naphthalenedicarboxamide and 0.05 wt % calciumstearate, 0.1 wt %tetrakis[methylene(3,5-di-t-butylhydroxyhydrocinnamate)]-methane and 0.1wt % tris-(2,4-di-t-butylphenyl)-phosphite, based on the sum of thepropylene polymers used, is melted in a twin screw extruder with atemperature profile of 100/145/190/215/225/205/190° C., homogenized,discharged and pelletized.

[0136] The resulting polypropylene polymer has a melt index of 1.2 g/10min at 230° C./2.16 kg, a tensile modulus of 1765 MPa and a Charpyimpact strength, notched, of 5.5 kJ/m² at −20° C.

[0137] 6.2. Manufacture of the Polyolefin Multilayer Pipe

[0138] For producing the 3-layer pipe, the pipe extruder of 1.2 wasused. The 60 mm extruder (temperature profile200/230/230/230/230/230/210/210° C.) for the intermediate layer was fedwith a blend of 70% by weight of a propylene homopolymer (melt index 0.8g/10 min at 230° C./2.16 kg, 4.2% by weight of ethylene) and 30% byweight of talcum, and both 50 mm side extruders (temperature profile180/200/225/225° C.) for the inner and outer layer were fed with theβ-nucleated propylene polymer of 6.1.

[0139] 6.2.1

[0140] The resulting 3-layer pipe, produced at a line speed of 1.0m/min, has an outer diameter of 110 mm and a wall thickness of 5.0 mm.The thickness of the outer layer was 1.0 mm, of the intermediate layer3.0 mm and of the inner layer 1.0 mm. Energy E_(D) was ≧490 Nm/m andring stiffness was 21.5 kN/m².

[0141] 6.2.2

[0142] A further 3-layer pipe, produced at a line speed of 1.0 m/min,has an outer diameter of 110 mm and a wall thickness of 4.2 mm.Thickness of the outer layer was 0.7 mm, of the intermediate layer 2.7mm and of the inner layer 0.8 mm.

[0143] Energy E_(D) was ≧420 Nm/m and ring stiffness was 12.2 kN/m².

1) polyolefin multilayer pipes where at least one of the layers of themultilayer pipe comprises a propylene homopolymer with melt indices of0.05 to 10 g/10 min at 230° C./2.16 kg or a propylene block copolymerfrom 90.0 to 99.9% by weight of propylene and 0.1 to 10.0% by weight ofα-olefins with 2 or 4 to 18 carbon atoms with melt indices of 0.05 to 15g/10 min at 230° C./2.16 kg, or mixtures thereof, wherein the propylenehomopolymer and/or propylene block copolymer are β-nucleated propylenepolymers and where the β-nucleated propylene homopolymer has anIR_(τ)≧0.98, a tensile modulus of ≧1500 MPa at +23° C. and a Charpyimpact strength, using notched test specimens, at −20° C. ≧3 kj/m² andwhere the β-nucleated propylene block copolymer has an IR_(τ) of thepropylene homopolymer block of ≧0.98, a tensile modulus of ≧1100 MPa at+23° C. and a Charpy impact strength ≧6 kJ/m² at −20° C. using notchedtest specimens and the multilayer pipe with a pipe diameter of less than0.25 m has an impact energy E_(D) (normalised) of at least 400 Nm/m anda ring stiffness S determined according to ISO 9969≧4 kN/m and amultilayer pipe a pipe diameter of ≧0.25 m has impact energy E of atleast 120 nm and a ring stiffness S determined according to ISO 9969≧4kN/m². 2) Polyolefin multilayer pipes according to claim 1 wherein themultilayer pipe with a pipe diameter of less than 0.25 m has an impactenergy E_(D) (normalised) of at least 600 Nm/m and a ring stiffness Sdetermined according to ISO 9969 ≧4 kN/m² and a multilayer pipe with apipe diameter of ≧25 m has impact energy E of at least 180 Nm and a ringstiffness S determined according to ISO 9969 ≧4 kN/m². 3) Polyolefinmultilayer pipe according to one of the claims 1 or 2, wherein theβ-nucleated propylene polymers with an IR_(τ)≧0.98 are propylenepolymers obtained by polymerization with a Ziegler-Natta catalyst systemcomprising titanium-containing solid components, an organoalumina,magnesium or titanium compound as cocatalyst and an external donoraccording to the formula R_(x)R′_(y)Si(MeO)_(4-x-y), wherein R and R′are identical or different and are branched or cyclic aliphatic oraromatic hydrocarbon residues, and y and x independently from each otherare 0 or 1, provided that x+y are 1 or
 2. 4) Polyolefin multilayer pipeaccording to claim 3, wherein the external donor isdicyclopentyldimethoxysilane. 5) Polyolefin multilayer pipe according toone of claims 1 to 4, wherein the β-nucleated propylene polymer contains0.0001 to 2.0 wt %, based on the polypropylenes used, dicarboxylic acidderivative type diamide compounds from C₅-C₈-cycloalkyl monoamines orC₆-C₁₂-aromatic monoamines and C₅-C₈-aliphatic, C₅-₈-cycloaliphatic orC₆-C₁₂-aromatic dicarboxylic acids, and/or diamine derivative typediamide compounds from C₅-C₈-cycloalkyl monocarboxylic acids orC₈-C₁₂-aromatic monocarboxylic acids and C₅-₈-cycloaliphatic orC₆-C₁₂-aromatic diamines, and/or amino acid derivative type diamidecompounds from amidation reaction of C₅-C₈-alkyl-, C₅-₈-cycloalkyl- orC₅-₁₂-arylamino acids, C₅-₈-alkyl-C₅-₈-cycloalkyl- or C₅-₁₂-aromaticmonocarboxylic acid chlorides and C₅-₈-alkyl-, C₅-C₈-cycloalkyl- orC₆-C₁₂-aromatic mono-amines, and/or quinacridone derivative compounds ofthe type quinacridone compounds, quinacridonequinone compounds, and/ordihydroquinacridone type compounds, and/or dicarboxylic acid salts ofmetals from group IIa of periodic system and/or mixtures of dicarboxylicacids and metals from group IIa of periodic system, and/or salts ofmetals from group IIa of periodic system and imido acids of the formula

wherein x=1 to 4; R=H, ═COOH, C₁-C₁₂-alkyl, C₅-₈-cycloalkyl orC₆-C₁₂-aryl, and Y=C₅-₁₂-alkyl, C₅-₈-cycloalkyl orC₆-₁₂-aryl-substituted bivalent C₈-₁₂-aromatic residues, as β-nucleatingagent. 6) Polyolefin multilayer pipe according to one of claims 1 to 5,wherein the multilayer pipe is a 3-layer pipe, wherein the outer andinner layer of the pipe comprises a β-nucleated propylene polymer andthe mid layer comprises a recycled propylene polymer, a propylenepolymer of higher stiffness than the β-nucleated propylene polymer, apropylene polymer containing fillers. 7) Polyolefin multilayer pipeaccording to one of claims 1 to 6, wherein the multilayer pipe is a2-layer pipe, wherein the outer layer of the pipe comprises aβ-nucleated propylene polymer and the inner layer comprises a recycledpropylene polymer, a propylene polymer of higher stiffness than theβ-nucleated propylene polymer, a propylene polymer containing fillers.8) Polyolefin multilayer pipe according to one of the claims 1 or 7,characterized in that the multilayer pipe is a smooth pipe with orwithout hollow sections. 9) Polyolefin pipe according to one of theclaims 1 or 8, characterized in that the multilayer pipe is a corrugatedor ribbed pipe with or without hollow sections. 10) A process forproducing polyolefin multilayer pipes by extrusion or injection moldingprocesses where at least one of the layers of the multilayer pipecomprises a propylene homopolymer with melt index of 0.05 to 10 g/10 minat 230° C./2.16 kg and/or block copolymers from 90.0 to 99.9 wt % ofpropylene and 0.1 to 10.0 wt % of α-olefins with 2 or 4 to 18 carbonatoms with melt indexes of 0.1 to 15 g/10 min at 230° C./2.16 kg,wherein the propylene homopolymers and/or propylene block copolymers areβ-nucleated propylene polymers and wherein the propylene homopolymerand/or the homopolymer block of the propylene block copolymer has anIR_(τ)≧0.98. 11) A process for producing polyolefin multilayer pipes ofclaim 11, wherein β-nucleated propylene polymers are propylene polymersproduced by melt mixing propylene homopolymers and/or propylenecopolymers with 0.0001 to 2.0% by weight, based on the polypropylenesused, β-nucleating agents at temperatures from 175 to 250° C. 12) Use ofpolyolefin multilayer pipes of any one of claims 1 to 10 for nonpressure pipe applications, preferably for outdoor use, for above aswell as underground drainage and sewerage pipe systems, surface waterpipes, pipes for cable protection, pipes for cold climate conditions andfor indoor use, soil and waste water pipes.